Balloon catheter and method for making same

ABSTRACT

In at least one embodiment of the present invention a balloon catheter is provided. The balloon catheter comprises a shaft having a lumen formed therethrough. Connected to the shaft is an inflatable balloon. The inflatable balloon has a balloon wall defining a balloon interior surface and a balloon exterior surface that is opposite the interior surface. In fluid communication with the balloon wall is the lumen for inflating the balloon to define an inflated state and for collapsing the balloon to define a deflated state. The balloon wall is textured in the deflated state such that the balloon interior surface is spatially registered with the balloon exterior surface. The balloon in the inflated state is tensioned to have a surface roughness substantially less than a surface roughness of the balloon in the deflated state.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.12/508,243, filed Jul. 23, 2009, and claims priority to and allavailable benefits of U.S. Provisional Application No. 61/083,730, filedon Jul. 25, 2008, and which is hereby incorporated by reference in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to medical catheters. More specifically,the invention relates to pushable balloon-tipped catheters and a methodfor making the balloon catheter.

2. Background

Pushable balloon-tipped catheters are used for the treatment of manyconditions relating to body vessels including arteries and veins. Forsuch treatments, a wire guide may be percutaneously inserted into thebody vessel and positioned near a location where treatment is necessary.The balloon catheter may be inserted through a guide catheter over thewire guide. The distal tip of the balloon catheter is guided to thetreatment location along the wire guide. Once at the treatment location,the balloon at the distal tip of the catheter is unfolded and inflated,such as for example, by pumping a mixture of saline and/or contrastsolution through the catheter into the balloon. When inflated, theballoon presses against the inner wall of the body vessel to dilate thevessel. If a stent is mounted on the balloon, inflation of the balloonwill also expand the stent to implant the stent within the artery. Afterthe vessel is dilated, the balloon is deflated to collapse the balloonback onto the shaft of the catheter for retraction into the guidecatheter and retrieval from the body vessel.

Sometimes difficulties may be encountered in retracting the deflatingballoon back into the guide catheter. These difficulties may beattributed to various factors, such as for example, the shape of theballoon, incomplete deflation of the balloon, and/or the balloon notreturning to its initial folded condition after deflation. Consequently,the force required to retract the balloon into the guide catheter may beunacceptably and/or undesirably high. Moreover, there may also be a riskthat the balloon will get caught against the distal end of the guidecatheter, making it difficult to remove the balloon catheter from thetreatment site.

Current methods for resolving some of these difficulties have been todesign balloon catheters with thinner, weaker balloon walls. Generally,a balloon having a thinner, weaker wall will present fewer difficultieson retraction from the body vessel than a balloon of the same shapehaving a thicker, stronger wall. However, the strength of a balloonwall, and more particularly the burst strength of the balloon wall, is acritical design parameter that may make reducing the balloon wallthickness impractical for lowering the force necessary to retract theballoon.

SUMMARY OF THE INVENTION

In at least one embodiment of the present invention, a balloon catheterfor deployment within a body vessel is provided. The balloon cathetercomprises a shaft having a lumen formed therethrough. Connected to theshaft is an inflatable balloon. The inflatable balloon has a balloonwall defining a balloon interior surface and a balloon exterior surfacethat is opposite the interior surface. In fluid communication with theballoon wall is the lumen for inflating the balloon to define aninflated state and for collapsing the balloon to define a deflatedstate. The balloon wall is textured in the deflated state such that theballoon interior surface is spatially registered with the balloonexterior surface. The balloon in the inflated state is tensioned to havea surface roughness substantially less than a surface roughness of theballoon in the deflated state.

In one aspect, the shaft has a proximal portion extending to a distalportion. The inflatable balloon is connected to the distal portion ofthe shaft. The texture of the balloon wall reduces force for collapsingthe balloon to facilitate retrieval of the balloon catheter from thebody vessel.

In at least one other embodiment of the present invention, acatheterization kit for use in the body vessel is provided. The kitincludes an introducer sheath having a proximal section extending to adistal section and a sheath lumen formed therethrough. A ballooncatheter as discussed in the foregoing paragraphs has an axial lengthdisposed within the sheath lumen of the introducer sheath for relativeaxial movement therein. A wire guide is provided that includes a distalpart disposed within the sheath lumen for relative axial movementtherein. The distal part of the wire guide is for being positionedadjacent to a treatment location within the body vessel to guide theballoon to the treatment location for treating thereto in the inflatedstate. The texture of the balloon wall reduces force for collapsing theballoon to facilitate the retraction of the balloon into the sheathlumen for retrieval of the balloon catheter from the body vessel.

In at least one other embodiment of the present invention, a method formaking a balloon catheter is provided. The method comprises blow moldinga heated resin within a mold to produce a balloon. The mold has aninternal mold surface that is textured to define a mold surface profilewith a corresponding mold surface roughness value. Blow molding of theheated resin includes forming a heated resin wall that has an exteriorresin surface facing the interior mold surface and an interior resinsurface that is opposite the exterior resin surface. The heated resinwall is pressurized such that the exterior resin surface conforms to thetexture of the internal mold surface and the interior resin surface isspatially registered with the exterior resin surface to define a heatedresin wall texture. The heated resin wall is cooled to form a balloonwall having a balloon texture which corresponds to the heated resin walltexture to define the balloon. The balloon is attached to a shaft toform the balloon catheter. The balloon is in fluid communication withthe shaft to be inflatable to tension the balloon, substantiallyreducing a surface roughness of the balloon.

Further objects, features, and advantages of the invention will becomeapparent from consideration of the following description and theappended claims when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of one embodiment of a catheterization kit for usein a body vessel according to the present invention;

FIG. 2 is an exploded view of the catheterization kit depicted in FIG. 1with a balloon catheter in an inflated state;

FIG. 3 a is a sectional view of the distal tip of the catheter kitdepicted in FIG. 1 along the line 3 a-3 a;

FIG. 3 b is a sectional view of the shaft of the catheterization kitdepicted in FIG. 1 along the line 3 b-3 b;

FIG. 4 is a diagram illustrating certain surface parameters;

FIG. 5 a is a random pattern texture in accordance with one embodimentof the present invention;

FIG. 5 b is a random pattern texture in accordance with anotherembodiment of the present invention;

FIG. 5 c is a random pattern texture in accordance with yet anotherembodiment of the present invention;

FIG. 5 d is a random pattern texture in accordance with one embodimentof the present invention;

FIG. 5 e is a random pattern texture in accordance with anotherembodiment of the present invention;

FIG. 5 f is a random pattern texture in accordance with yet anotherembodiment of the present invention;

FIG. 6 a is a repeating pattern texture in accordance with oneembodiment of the present invention;

FIG. 6 b is a repeating pattern texture in accordance with anotherembodiment of the present invention;

FIG. 6 c is a repeating pattern texture in accordance with yet anotherembodiment of the present invention;

FIG. 6 d is a repeating pattern texture in accordance with oneembodiment of the present invention;

FIG. 6 e is a repeating pattern texture in accordance with anotherembodiment of the present invention;

FIG. 7 is a sectional view of a balloon for the balloon catheter beingblow molded in a mold in accordance with one embodiment of the presentinvention;

FIG. 8 a is an enlarged sectional view of a balloon wall in a mold inaccordance with an embodiment of the present invention;

FIG. 8 b is an enlarged sectional view of the balloon wall in accordancewith one embodiment of the present invention;

FIG. 9 a is an enlarged sectional view of the balloon wall in a deflatedstate in accordance with an embodiment of the present invention;

FIG. 9 b is an enlarged sectional view of the balloon wall in aninflated state in accordance with an embodiment of the presentinvention;

FIG. 10 a is a side view of a deflated, folded balloon in accordancewith one embodiment of the present invention;

FIG. 10 b is a sectional view of the deflated, folded balloon depictedin FIG. 10 a along the line 10 b-10 b; and

FIG. 11 is a flow-chart describing an example method for making theballoon catheter according to the present invention.

DETAILED DESCRIPTION

Detailed embodiments of the present invention are disclosed herein. Itis understood however, that the disclosed embodiments are merelyexemplary of the invention and may be embodied in various andalternative forms. The figures are not necessarily to scale; somefigures may be configured to show the details of a particular component.Therefore, specific structural and functional details disclosed hereinare not to be interpreted as limiting but merely as a representativebasis with the claims and for teaching one skilled in the art topractice the present invention.

Referring now to FIGS. 1-3 b, a pushable balloon catheterization kit inaccordance to one embodiment of the present invention is illustratedtherein and designated at 10. The kit 10 includes a balloon catheter 12.The balloon catheter 12 comprises a shaft 14 having a proximal portion16 extending to a distal portion 18. An inflatable balloon 24 iscooperable with the distal portion 18 of the shaft 14.

The shaft 14 and the inflatable balloon 24 may be made of anyappropriate flexible material for use as a catheter. The material mayinclude, for example, nylon, polyester, polytetrafluoroethylene (PTFE),latex, rubber, and mixtures thereof.

In one embodiment, the balloon 24 is made from a low or non-compliantmaterial, such as for example, nylon or polyester. The compliantcharacteristics of the balloon 24 affect how the physician may use theballoon catheter 12. A low or non-compliant balloon will increase indiameter by up to a maximum of about 5% of its normal diameter inresponse to increasing the pressure for inflating the balloon 24 tobetween about 5 to 20 atmospheres. One example use for the low ornon-compliant balloon 24 may be to dilate it for cracking lesions withina restricted portion of the body vessel while minimizing the likelihoodof damaging an adjacent non-restricted portion of the body vessel.Alternatively, the balloon 24 may be made from a hybrid or highlycompliant material where the diameter of the balloon may increase asmuch as about 40% during inflation. The hybrid or highly compliantballoon 24 may proportionally increase in diameter in response toincreases in inflation pressure which may allow for fewer balloon sizesto be used to treat a wider range of vessel diameters.

The shaft 14 as illustrated in FIGS. 3 a and 3 b may include an outerlumen 20 and an inner lumen 22. The outer and inner lumens 20 and 22extend from the proximal portion 16 towards the distal portion 18 andmay be defined by first and second walls 21 and 23, respectively. In oneexample, the second wall 23 extends distally beyond the first wall 21.The inflatable balloon 24 is in fluid communication with the outer lumen20 and the second wall 23 may extend at least to the distal end of theballoon 24 so that the inner lumen 22 is not in fluid communication withthe balloon 24.

The balloon 24 has a balloon wall 26 comprising a balloon interiorsurface 28 and a balloon exterior surface 30 that is opposite theballoon interior surface 28. In one embodiment, the balloon 24 has aproximal balloon aperture 32 and a distal balloon aperture 34. Theproximal and distal balloon apertures 32 and 34 are cooperable with thedistal portion 18 of the shaft 18 and attach thereto at axial locations36 and 38. As illustrated, the balloon 24 attaches to the first wall 21of the shaft 14 at axial location 36 and to the second wall 23 of theshaft 14 at axial location 38. The balloon 24 may be attached to theshaft 14 by any suitable means, such as for example, hot melt bonding,adhesive bonding, solvent bonding or ultrasonic welding.

In this embodiment, at the proximal end 16 of the shaft 14 is aninjection port 40 as depicted in FIGS. 1 and 2. The injection port 40provides access for injecting a fluid to be advanced through the outerlumen 20 to the balloon 24 for inflating the balloon 24 to define aninflated state 42 (shown in phantom in FIG. 3 a). The fluid may also beremoved from the balloon 24 through the outer lumen 20 and the injectionport 24 to collapse the balloon 24 to define a deflated state 44. In oneexample, the balloon 24 in the inflated state 42 has an internalpressure of at least about 5 atmospheres and the balloon 24 in thedeflated state 44 has a pressure of less than about 5 atmospheres andpreferably between about 0 and 1 atmosphere (0.0 to 14.7 psi or −14.7 to0.0 psig).

As shown in FIGS. 1 and 3 a, the wall 26 of the balloon 24 is textured50 in the deflated state 44. In one example, the texture 50 of a balloonwall 26 in the deflated state 44 corresponds to a random grain pattern,several examples of which are illustrated in FIGS. 5 a-5 f. In anotherexample, the texture 50 of the balloon wall 26 in the deflated state 44corresponds to a repeating grain pattern, several examples of which areillustrated in FIGS. 6 a-6 e.

The catheterization kit 10 is shown in FIGS. 1 and 2, for example, aspart of a catheterization system for treatment of the body vessel inaccordance with one embodiment of the present invention. The deliverysystem may include a PTFE introducer sheath 80 for percutaneouslyintroducing the kit 10 into a body vessel. Of course, any other suitablematerial for the introducer sheath 80 may be used without falling beyondthe scope or spirit of the present invention. The introducer sheath 80may have any suitable size, such as for example, between about 3 Frenchto 8 French. The introducer sheath 80 serves to allow the ballooncatheter 12 to be percutaneously inserted into a desired location in thebody vessel. The introducer sheath 80 receives and provides stability tothe balloon catheter 12 at a desired location of the body vessel. Forexample, the introducer sheath 80 is held stationary within a commonvisceral artery, and adds stability to the balloon catheter 12 as it isadvanced through the introducer sheath 80 to desired treatment locationin the vasculature.

The kit 10 may also include a wire guide 82 configured to bepercutaneously inserted within the vasculature to guide the ballooncatheter 12 to the desired location. The wire guide 82 may bemanipulated through a wire guide port 84 of the balloon catheter 12where the inner lumen 22 is fed over the wire guide 82 to provide theballoon catheter 12 with a path to follow as it is advanced within thebody vessel.

When the distal tip 64 of the balloon catheter 12 is at the desiredlocation in the body vessel, the wire guide 82 may optionally beremoved. The balloon 24 may then be inflated to the inflated state 42for treating the body vessel. After treatment of the body vessel, theballoon 24 is retracted by collapsing the balloon 24 and retracting theballoon 24 into a lumen of the sheath 80 for retrieval of the ballooncatheter 12 from the body vessel in the deflated state 44. As will bediscussed in further detail below, the texture 50 of the balloon wall 26in at least one embodiment reduces the force for collapsing the balloon24 to facilitate retraction of the balloon 24 into the lumen of thesheath 80.

Referring to FIG. 4, further details regarding texture and surfaceroughness in accordance with at least one embodiment of the presentinvention are provided. A surface 52 may have a regular or irregulararray of peaks 54 and valleys 56. A reference mean surface or surfacecenterline 58 is a datum surface that runs centrally through the peaks54 and valleys 56 to divide the surface profile 52 so as to encloseequal areas above and below the surface centerline 58. Reference to thesurface centerline 58 is used to measure the roughness of the surface52. One particular type of surface roughness measurement is a numericalroughness average value (S_(a)) which is an arithmetic average of theabsolute values of the deviations of the surface 52 from the surfacecenterline 58 as measured normal to the surface centerline 58(Note—R_(a) is a one-dimensional equivalent of S_(a), e.g., when surface52 is measured in one direction relative to a center line included inthe surface centerline 58). The roughness average (S_(a)) may beexpressed in microns (μm).

Referring also to FIGS. 8 a and 8 b, the texture 50 of the balloon wall26 is such that the balloon interior surface 28 is spatially registeredwith the balloon exterior surface 30 providing corresponding surfaceprofiles 46 and 48 with substantially matching surface roughness values.Spatially registered is hereinafter understood to mean that the surfaces28 and 30 are substantially matched on opposing sides of the wall 26.For example, the surfaces 28 and 30 are corrugated, micro-corrugated orsubstantially parallel such that when measures by a surface profiler,e.g. Micro Photonics Nanovea 3D Profilometer™, with the measured surfacefacing upward, peaks 54 on the exterior surface 30 are opposite valleys56 on the interior surface 28 and valleys 56 on the exterior surface 30are opposite peaks 54 on the interior surface 28. Moreover,“substantially matching” is hereinafter understood to mean matching towithin at least 40%. For example and as illustrated in FIG. 8 b, aninterior surface 28 that substantially matches an exterior surface 30will have valley depths 57 and peak heights 55 that correspond to atleast 40% of the peak heights 55 and valley depths 57 of the exteriorsurface 30 (note—peak heights and valley depths are measure relativetheir corresponding surface centerline 58. Moreover, substantiallymatching surface roughness values for the interior and exterior surfaces28 and 30 is hereinafter understood to mean that the magnitude of thesurface roughness values of the interior surface 28 are at least 40% ofthe corresponding magnitude of the surface roughness values of theexterior surface 30 (using the absolute values for the surface roughnessvalues to account for any opposing directional effects due to thespatially registered peaks and valleys).

In an example of the balloon 24 in the deflated state 44, the surfaceroughness value of the exterior surface 30 is at least an averageroughness (S_(a)) of about 2 microns and preferably, is about 3 micronsor more. Moreover, the surface roughness value of the balloon interiorsurface 28 is at least an average roughness (S_(a)) of about 1.5microns. Preferably in this example, a ratio of the surface roughnessvalue of the balloon exterior surface 30 to the surface roughness valueof the balloon interior surface 28 does not exceed about 2:1.

In one example of the balloon in the inflated state 42, the balloon wall26 is tensioned such that the texture 50 is substantially smoothed ornearly eliminated, thereby reducing the surface roughness of both theballoon interior and exterior surfaces 28 and 30 relative to thesurfaces 28 and 30 in the deflated state 44. Applicants have found thatby texturing the balloon wall 26 such that the texture 50 is prominentin the deflated state 44 but significantly diminishes in the inflatedstate 42 only to become prominent again when the balloon 24 issubsequently deflated, that the column strength of the balloon 24 may besignificantly reduced without substantially decreasing the burststrength of the balloon 24. This modulating texture 50 of the balloonwall 26 preferably reduces the force for collapsing the balloon 24,facilitating retrieval of the balloon catheter 12 from the body vessel.The balloon 24 of the present invention may be configured at variousnominal thicknesses D including nominal thicknesses in the range ofabout 0.0005 in to 0.0025 in, which provided suitable results incombination with the modulating texture 50 for reducing the columnstrength of the balloon 24 without substantially decreasing its burststrength.

In one embodiment, the surface roughness value of the exterior surface30 of the balloon 24 in the inflated state 42 is reduced by at leastabout 50% from the surface roughness value of the exterior surface 30 inthe deflated state 44. In another embodiment, the surface roughnessvalue of the balloon interior surface 28 in the inflated state 42 isreduced by at least about 50% from the surface roughness value of theinterior surface 28 in the deflated state 44.

Referring to FIGS. 9 a and 9 b, at least one other embodiment of thepresent invention is provided. The rough profile or texture 50 of theexterior balloon surface 30 in the deflated state 44 may be used totransfer medicants 60 to a treatment site in the body vessel.Specifically, the volume created between the valleys 56 and the peaks 54in the surface 30 represent potential sites for the deposit of variousbioactive materials which may be delivered to a stenosis or other bodylocation. Medicants 60 such as Paclitaxel, Sirolimus, and Everolinus, orother commonly known medicants may be used to minimize restenosis of thebody vessel. The medicants 60 can be coated onto the surface 30 of theballoon 24 while in the deflated state 44, filling in the texture 50.Upon inflation within the body vessel to the inflated state 42, theexterior balloon surface 30 is smoothed by the tensioning of the balloonwall 26 so that the valleys 56 and the peaks 54 diminish, therebyforcefully implanting the medicants 60 into the treatment area, e.g.,stenosis, of the body vessel.

Referring to FIGS. 10 a and 10 b, at least one other embodiment of thepresent invention is provided. The balloon 24 has a proximal balloon end62 and a distal balloon end 64 and a longitudinal axis 66 extendingbetween the proximal and distal balloon ends 62 and 64. The balloon 24may be folded in the deflated state 44 to provide a low profileconfiguration for being advanced into the body vessel for deploymenttherein. In one example, the balloon 24 is folded so as to form at least3 folded portions 68, 70 and 72 extending between the proximal anddistal balloon ends 62 and 64. The folded portions 68, 70 and 72 may befolded about the longitudinal axis 66 either clockwise orcounter-clockwise. When the balloon 24 is deployed, the folded portions68, 70 and 72 unfold about the longitudinal axis 66 thereby allowing theballoon 24 to expand to the inflated state 42.

Referring to FIGS. 7, 8 a and 11, a method for making a balloon catheterin accordance with at least one embodiment of the present invention isprovided. The method comprises blow molding a heated resin at 102 withina mold 86 to produce a balloon 24. The resin may be heated via heatersor viscous dissipation, e.g., working of the resin through the moldingprocess, or any other suitable means for heating the resin. The heatedresin may be nylon or PET at a temperature at or above its respectiveglass transition T(g) or melting point T(m). Any other polymer suitablefor blow molding may also be used.

The mold 86 has an internal mold surface 88 that is textured. The shapeof the internal mold surface 88 correspond to the intended shape of theballoon 24 which is typically configured as a surface that has beenrotated about its longitudinal axis 66. In one example, the balloon 24has a shape that includes a cylindrical section 90, and proximal anddistal frustoconical end sections 92 and 94.

As the mold is heated, air is blown into the tubular blank of heatedresin to form a heated resin wall at 104 that may be shaped as a bubblehaving an exterior resin surface 87 facing the internal mold surface 88and an opposed interior resin surface 89 positioned inside of thebubble. The heated resin is further pressurized at 106 by the air(sometimes referred to as packing-out) such that the exterior resinsurface 87 conforms to the texture of the internal mold surface 88 andthe interior resin surface 89 is spatially registered with the exteriorresin surface 87 to define a heated resin wall texture. Notably, thetemperature of the heated resin relative to its T(g) or T(m) and theamount of pressurizing affects the extent to which the exterior resinsurface 87 conforms to the texture of the mold surface 88 and the extentto which the interior resin surface 89 becomes spatially registered withthe exterior resin surface 87.

The heated resin wall is then cooled at 108 to form the balloon wallhaving a balloon texture which corresponds to the heated resin walltexture. The wall thickness of the finished balloon 24 is determined bythe interaction of various factors, including the wall thickness of theheated resin blank, the external diameter of the finished balloon 24,the temperature and rate of change of temperature of the mold 86, thestretching and tensioning of the heated resin wall and the pressure andrate of change of pressure of the air blown into the heated resin blank.

The internal mold surface 88 is textured with a carefully selected grainpattern to provide a targeted surface roughness average value for themold surface 88. The roughness of the mold surface 88 will typically begreater than the roughness of the finished balloon 24 (See FIG. 8 a). Inone example, a balloon 24 having an exterior surface 30 with a roughnessaverage (S_(a)) of 3 microns is molded in a mold 86 having an internalmold surface 88 with a roughness average (S_(a)) of at least about 6microns.

Applicant has also found that the method for graining the mold 86 mayinfluence the effectiveness of the modulating texture 50 to reduce thecolumn strength of the balloon 24 without substantially decreasing itsburst strength. Specifically, both chemical etching and electricaldischarge machining (EDM) where used to grain different mold surfaces88. Chemically etching is a process where the mold surface 88 isselectively etched with an acid solution to provide a texture. Grainpatterns using this method may have a more repeating pattern asillustrated in FIGS. 6 a-6 e. Alternatively, EDM or spark erosion movesan eroding electrode relative to the mold surface 88 to create aplurality of random arc formations therebetween to produce a texture onthe surface 88. Grain patterns using this method may have a more randompattern as illustrated in FIGS. 5 a-5 f. Both processes result in amicron level texture being formed thereon. However, Applicant found thatthe balloons 24 that were textured with a more random grain patternrequire less force for collapsing than balloons 24 that were texturedwith a more repeating pattern. The surface roughness values of therandom and repeating grain patterns used were the same.

The method further comprises attaching at 110 the balloon 24 to theshaft 14 to form the balloon catheter 12. The balloon 24 may be attachedat its proximal and distal ends 62 and 64 by being hot melted,adhesively bonded or solvent fused to the distal portion 18 of the shaft14. Any other suitable means known to those skilled in the art may alsobe used to attach the balloon 24 to the shaft.

To further illustrate examples of the present invention, two series oftests will now be discussed. Provide below are tables 1a-1c thatsummarize a first series of tests which includes sheath compatibilitytesting and the force required for collapsing balloons which were moldedin different surface finished molds. One mold had a polished surface(typically used for medical molding balloons), and the two other moldswere finished with random surface patterns having surface roughnessaverages (R_(a)) of 6 μm and 12 μm respectively. The proximal and distaltaper results correspond to the force required for collapsing theproximal and distal frustoconical sections 92 and 94 of the balloon 24into the sheath 80. The test results indicate that the balloons moldedin higher surface roughnesses molds required significantly less forcefor being collapsed into the sheath than balloons molded in lowersurface roughnesses or smoothly polished molds. Specifically, balloonsmolded in the 12 R_(a) mold required an average of 1.93 lbf to collapsethe distal tapers, representing the highest force required for retrievalof the balloons, while balloons from the 6 R_(a) mold and the smoothmold required an average of 2.18 lbf and 2.62 lbf, respectively, tocollapse the distal tapers.

TABLE 1a Sheath Compatibility test Smooth Polished Mold Sample InfoSheath Quantitative Results (lbf) Sample Lot Size Proximal Distal Within# Size # Used (fr) Taper Taper Sheath Comments 1 8-4 P1824790 6 1.653.00 1.35 Average balloon dwall = .0805 mm 2 8-4 P1824790 6 2.65 2.451.50 Average balloon dwall = .0805 mm 3 8-4 P1824790 6 1.70 2.40 1.50Average balloon dwall = .0805 mm Averages 2.00 2.62 1.45

TABLE 1b Sheath Compatibility test 6 Ra mold (random EDM pattern) SampleInfo Sheath Quantitative Results (lbf) Sample Lot Size Proximal DistalWithin # Size # Used (fr) Taper Taper Sheath Comments 1 8-4 P1889196 61.30 2.45 1.55 Average balloon dwall = .0795 mm 2 8-4 P1889196 6 1.652.15 1.35 Average balloon dwall = .0795 mm 3 8-4 P1889196 6 1.20 1.951.15 Average balloon dwall = .0795 mm Averages 1.38 2.18 1.35

TABLE 1c Sheath Compatibility test 12 Ra mold (random EDM pattern)Sample Info Sheath Quantitative Results (lbf) Sample Lot Size ProximalDistal Within # Size # Used (fr) Taper Taper Sheath Comments 1 8-4P1899197 6 1.05 2.00 1.25 Average balloon dwall = .083 mm 2 8-4 P18991976 1.15 1.85 0.90 Average balloon dwall = .083 mm 3 8-4 P1899197 6 0.851.95 0.95 Average balloon dwall = .083 mm Averages 1.02 1.93 1.03

In a second series of tests summarized below in tables 2a-2b balloonswith different surface roughness textures were evaluated. The balloonswere measured using a variety of different surface roughnessmeasurements when in the deflated and inflated states. A Micro PhotonicsNanovea 3D Profilometer™ surface profiler unit was used to make thevarious measurements on the balloons. Group A and group B were texturedballoons in the deflated state that were molded in molds having surfaceprofiles with a surface roughness R_(a) of 12 μm and 2 μm respectively.Group C and group D were textured balloons inflated to between about 1atmosphere (14.7 psig) and 12 atmospheres (176.4 psig) gauge pressure asindicated and were molded in molds having surface profiles with asurface roughness R_(a) of 12 μm and 2 μm respectively. The surfaceroughness measurement used to characterize the texture of these balloonswere the Sq (root mean square height), Ssk (skewness), Sku (kurtosis),Sp (maximum peak height), Sv (maximum pit height or valley depth), Sz(maximum height), Sa (arithmetic mean height, Sdq (root mean squaregradient), Sds (density of summits) and Spd (density of peaks).

The textured balloons molded in molds having a surface profile with asurface roughness of R_(a) 12 μm (groups A and C) performed better thantextured balloons molded in molds having a surface profile with asurface roughness of R_(a) 2 μm (groups B and D). However, all of thetextured balloons performed in accordance with the present invention andrequired less force for collapsing than balloons molded in conventionmolds with smooth surface profiles, e.g., balloons tested and reportedin Table 1a.

It is believed that several of the different types of surface roughnessmeasurements provided below facilitate identifying textures whichperform in accordance with the present invention. For example, the S_(a)values for the OD (outer surface) and the ID (internal surface) of thegroup A and B balloons are 4.74 and 4.43 μm, and 1.47 and 1.41 μmrespectively. In both groups, the S_(a) average in the deflated state ofthe ID nearly matches (within 90%) that of the OD.

In another example, the Ssk or skewness may be used to determine if thetexture of the balloon in the deflated state is “spatially registered.”Specifically, the Ssk describes the asymmetry of the height distributionhistogram. That is, if the Ssk=0, then a symmetric height distributionis indicated, if the Ssk >0, then a higher peak distribution isindicated, e.g., flat surface with peaks, and if Ssk <0, then a highervalley distribution is indicated, e.g., flat surface with pits. The Sskof the OD and ID of the group A and B balloons are −0.631 and 0.613, and−0.28 and 0.235 respectively. This indicates that the OD's for both thegroup A and B balloons have higher valley distributions while theirrespective ID's have higher peak distributions. Notably, when the Ssk ofthe OD and the ID are combined within each group the sum is near zero,indicating that the peak and valley distributions of the opposingsurfaces is practically matched (e.g. group A, the Ssk sum is−0.631+0.613=−0.018). This near zero value for the sum of the Ssk valuesof the opposed surfaces indicates that the surfaces are spatiallyregistered.

In yet another example, the Sku or kurtosis may be used to describe thepeakedness and randomness of the balloon's textured surface.Specifically, a Sku value of 3 indicates a perfect Gaussian randomsurface pattern. The further a value is from 3 (e.g., lower or higherthan 3) the less random the surface pattern. Moreover, a high Sku valueindicates a high proportion of the surface profile heights fallingwithin a narrow range of heights, e.g., a compressed profile. Notably,the Sku values of the OD and ID of the group A and B balloons are 3.45and 3.41, and 2.94 and 2.77 respectively. This indicates that theballoons of group A and group B have surface texturing patterns that arevery random. Also, the Sku values for the group C and D balloons (onlyOD measurements were made on the groups C and D balloons) increasedsteadily when the balloons were inflated from 1 atmosphere gaugepressure to 8 or 12 atmospheres gauge pressure (e.g., Sku of 8.78 forgroup C balloons at 12 atm gauge pressure and Sku of 15 for group Dballoons at 8 atm gauge pressure), indicating that the balloons wereflattening or smoothing out, e.g., the respective textures modulated. Inone embodiment, balloons in the deflated state are textured with asurface profile having Sku values between about 2.0 and 4.0.

In another example, the Sds or density of summits may be used todescribe the number of local maximum peaks per area. The Sds is similarto the Spd or density of the peaks, but uses a more sensitive EUR 15178Ntesting standard. Specifically, the Sds considers a peak a maximum onlyif it is higher than its 8 neighboring peaks. This is a spatialparameter which is indicative of peak spacing. The larger the Sds valuesthe further the maximum peaks are to one another. In one embodiment, Sdsvalues between about 50 and 1000 are preferred for the textures ofballoons in the deflated state. Notably, the Sds values for the OD andID of the group A and B balloons are 180 and 102, and 449 and 574respectively. Also, as the balloons are inflated, as in the group C andD balloons, the Sds values significantly increase, illustrating themodulating texture or smoothing of the balloons surfaces, e.g., Sds of2948 per mm² for the group C balloons at 12 atm gauge pressure and 4001per mm² for the group D balloons at 8 atm gauge pressure.

TABLE 2a Raw Balloon Material Group A, 12 Ra, Group B, 2 Ra, Height 10 ×4 12 × 8 Smooth/Polished Mold, Parameters Description Unit OD ID OD IDOD ID Sq Root mean square μm 5.95 5.66 1.82 1.75 0.237 0.176 height SskSkewness — −0.631 0.613 −0.28 0.235 −0.238 0.553 Sku Kurtosis — 3.453.41 2.94 2.77 3.83 5.17 Sp Maximum peak height μm 13.4 20.5 5.35 5.622.09 2.36 Sv Maximum pit height μm 27.3 11.8 9.16 4.45 1.12 1.12 SzMaximum height μm 40.7 32.3 14.5 10.1 3.21 3.48 Sa Arithmetic meanheight μm 4.75 4.43 1.47 1.41 0.186 0.136 Hybrid Parameters Sdq Rootmean square — 0.183 0.144 0.104 0.0583 0.0479 0.0455 gradient SdsDensity of summits 1/mm{circumflex over ( )}2 180 102 449 574 5428 5981Featured Parameters Spd Density of peaks 1/mm{circumflex over ( )}2 1428 29 36 601 606

TABLE 2b Finished Catheters Under Pressure (OD measurements only) GroupC, 12 Ra, 8 × 4 Description Unit 1 atm 8 atm 12 atm Height Parameters SqRoot mean square μm 3.75 0.624 0.293 height Ssk Skewness — −0.669 −1.28−1.7 Sku Kurtosis — 3.62 5.64 8.78 Sp Maximum peak height μm 13.1 1.20.861 Sv Maximum pit height μm 16.8 3.58 2.31 Sz Maximum height μm 304.79 3.17 Sa Arithmetic mean height μm 2.96 0.473 0.215 HybridParameters Sdq Root mean square — 0.138 0.0293 0.0188 gradient SdsDensity of summits 1/mm{circumflex over ( )}2 295 1770 2948 FeaturedParameters Spd Density of peaks 1/mm{circumflex over ( )}2 17 13 15Group D, 2 Ra, 12 × 8 Description Unit 1 atm 4 atm 8 atm HeightParameters Sq Root mean square μm 0.316 0.212 0.0914 height Ssk Skewness— −1.22 −1.69 −2.35 Sku Kurtosis — 5.42 8.07 15 Sp Maximum peak heightμm 0.655 0.47 0.407 Sv Maximum pit height μm 2.1 1.65 1.22 Sz Maximumheight μm 2.76 2.12 1.63 Sa Arithmetic mean height μm 0.242 0.153 0.0612Hybrid Parameters Sdq Root mean square — 0.0234 0.0227 0.014 gradientSds Density of summits 1/mm{circumflex over ( )}2 2161 3707 4001Featured Parameters Spd Density of peaks 1/mm{circumflex over ( )}2 2863 44

As a person skilled in the art will readily appreciate, the abovedescription is meant as an illustration of the implementation of theprinciples of this invention. This description is not intended to limitthe scope or application of this invention in that the invention issusceptible to modification, variation, and change, without departingfrom the spirit of this invention, as defined in the following claims.

1. A method of making a balloon catheter comprising: blow molding aheated resin within a mold to produce a balloon, the mold having aninternal mold surface textured to define a mold surface profile with acorresponding mold surface roughness value, the blow molding including:forming a heated resin wall that has an exterior resin surface facingthe internal mold surface and an interior resin surface opposite theexterior resin surface; pressurizing the heated resin wall such that theexterior resin surface conforms to the texture of the internal moldsurface and the interior resin surface is spatially registered with theexterior resin surface, defining a heated resin wall texture; andcooling the heated resin wall to form a balloon wall having a balloontexture which corresponds to the heated resin wall texture, defining theballoon; and attaching the balloon to a shaft to form the ballooncatheter, the balloon in fluid communication with the shaft to beinflatable to tension the balloon, substantially reducing a surfaceroughness of the balloon.
 2. The method according to claim 1 wherein themold surface roughness value is at least a numerical average surfaceroughness value (R_(a)) of about 6 microns.
 3. The method according toclaim 1 wherein the texture of the internal mold surface corresponds toa random grain pattern formed by electrical discharge machining themold.
 4. The method according to claim 1 wherein the texture of theinternal mold surface corresponds to a repeating grain pattern formed bychemically etching the mold.